CONTRIBUTING.md: Update argument input parameter.

Change-Id: Ia7f7065a2a1f4fa714149e622d4f69574879145b
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 2a28196..c0258c5 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -147,7 +147,7 @@
         ```
         Get URL List
             [Documentation]  Return list of URLs under given URL.
-            [Arguments]  ${openbmc_url}
+            [Arguments]  ${openbmc_url}  ${policy}
 
             # Description of argument(s):
             # openbmc_url  URL for list operation (e.g.